My pond snails never did but they never lasted long enough with my fish and I had very few plants. I would guess you have some lighting and/or nutrient deficiencies.
they will only eat dead or decaying plant matter. even when starved they wouldnt go for live and healthy plants. i would go with what jpappy789 said and look into your lighting and/or nutrient deficiencies.
I agree with the previous posters, the only time I see damage to any of my plants is when they are on their way out. Healthy plants are typically not eaten.